C2-427/390 hesitation

[Robert M.]

My 67 427/390 runs great. It has a M20 wide box with a 3.08 rear. The only annoyance is when I pull out from a stop it tends to stumble or fall flat. Does this sound like and issue with the Holley carb such as accelerator pump or float adjustment? No other problem and at cruise,WOT or any other time it runs fine.

[Joe L.]

Re: C2-427/390 hesitation

Rob----

I would say it's a carb problem just as those you mentioned. At least, that's the very first thing I would look into.

[Robert M.]

Re: C2-427/390 hesitation

Thanks Joe, that's what I will look at first. I was looking for confirmantion as to what I thought it was/

[Jim T.]

Re: C2-427/390 hesitation

The clearance of between the accelerator pump lever and the carb linkage is very small to allow for instant pumping of gas into the carb above the throttle plates to prevent stumble or falling flat. The accelerator pump may also require replacement. After running the engine, turn it off. Remove the air cleaner. Open the throttle plates observing the two nozzles squirt gas. If it is not a steady strong stream during the movement of the throttle plates there could be a restriction of the flow from the accelerator pump. There is rubber flow control valve that is installed in the metal of the fuel bowl that prevents the accelerator pump action from pumping fuel back into fuel bowl when the pump action is used when accelerating. The flow control valve allows fuel to enter the cavity. It may not be sealing like it should.

[Robert M.]

Re: C2-427/390 hesitation

Thanks Jim.very specific and informative. I am not the mechanicla type to that extent but will have the mechanic take a look.

[Robert M.]

Re: C2-427/390 hesitation

It just dawned on me(senior moment) that I neglected to mention that the engine is not completely stock. It has a hydraulic roller cam kit that is mildly more aggressive then the orignal stock cam.